What is the definition of a strike price in a stock option?

Strike price is commonly used during stock options trading. It is a price at which an investor comes in, meaning the bought price. 

The strike price is part of an option contract which specifies the level at which the option holder may buy (call) or sell (put) the underlying asset. 

Other ways to define the strike price in the stock market. 

The prices fixed by the seller of security after receiving bids in a tender offer, typically for a sale of bonds or a new stock market issue. The price at which a put or call option can be exercised.